Office Christmas Party is not a terrible comedy, but it’s not a great one, either. Unlike the last two Zack Galifianakis movies, Keeping Up with the Joneses and Masterminds, Office Christmas Party is a tolerable comedy. It’s an easy movie to watch and hard to dislike, but not good enough to recommend. It’s an airplane movie. It’s a time killer if you’re in a two-theater mall on a Saturday afternoon. It’s fine.

Much of the reason it rises to the level of fine is Kate McKinnon, who plays an obnoxious, rule-following HR Manager who — over the course of the movie — begins to awaken to her wild side. Her character is insufferable through the first half of the film, but by the last half hour, she is the best — and maybe only — real reason to watch. She’s a goddamn delight.

The premise is this (and for the purposes of this review, I’ll use real names instead of character names to reduce confusion): T.J. Miller runs a branch of a tech company that is struggling. His sister, Jennifer Aniston — the interim CEO of the company — threatens to shut down the branch and fire everyone if Miller can’t close a deal with a salesman with another company, Courtney B. Vance. All things being equal, Courtney B. Vance prefers a company with a better work culture. Miller, along with the branch manager, Jason Bateman, and the lead tech, Olivia Munn, decide to throw a huge rager to win the client’s business.

Rob Corddry plays an obnoxious customer service representative; Vanessa Bayer plays the mothering receptionist slash single mom; Randall Park plays an accountant with a babying fetish; Karan Soni plays a tech guy who hires a prostitute (pimped out by Jillian Bell) to prove to his douchebag friends that he has a girlfriend; and Veep’s Sam Richardson plays a straight-laced employee turned wild DJ.

The first act is a slow-build toward a party that never seems to arrive, and once it does in the second act, it’s not as fun as we’d like it to be. The movie doesn’t gain much momentum during the party, either, and only begins to take off in the third act, after the party has failed and T.J. Miller heads off with Jillian Bell’s homicidal pimp, forcing McKinnon to take action and Aniston to show off her martial arts skills. Even then, save for McKinnon and Bell, it’s only pleasantly middling.

But it’s not a disaster. It’s not Sandlerian. It’s basically what we’ve come to expect from Jon Lucas and Scott Moore: It’s 21 and Over with older characters. It’s not as good as The Hangover but slightly better than its sequels. It’s about as good as their Bad Moms with McKinnon instead of Kathryn Hahn stealing the show, which is to say: Amiably diverting, thanks to a likable cast, but it’s never as funny as it needs to be.

Dustin is the founder and co-owner of Pajiba. You may email him here or follow him on Twitter.